Smoke pipe damper



.w. HODGINS 3,010,451

SMOKE PIPE DAMPER Nov. 28, 1961 ELECTRICALLY AND I ,HYDRAUL|CALLY OPERATED TIME LAG MOTOR I l I L l "K FIG. l. #7

I I I I I I, \i l I 8 TRANSFORM R T ERMOSTAT /DAMPER VALVE MOTOR '-11 3 fi-I 31 F G.3.' Z 23 P/RCIIRCIJQ$;OBLURNER MICRO SWITCH SAFETY LIMIT i Q CONTROL 26 L v 27 BURNER I Inventor IGNITION 28 I mum: HODGIHS BURNER 29 j h g d- MOTOR M Attorney Nov. 28, 1961 w. HODGINS 3,010,451

SMOKE PIPE DAMPER Filed Nov. 28, 1958 2 Sheets-Sheet 2 Invcntor WILLIAM HODG-INS Attorney United States Patent C i 3,010,451 SMOKE PIPE DAMPER William Hodgins, Ottawa, Ontario, Canada, assignor to Hodgins Combustion Devices Limited, Ottawa, Ontario, Canada, a company of Canada Filed Nov. 28, 1958, Ser. No. 776,857 2 Claims. (Cl. 126-285) This invention concerns a smoke pipe damper, relating especially to one that is motor actuated.

In many furnaces, particularly those intermittently fired with oil and gas fuels, a serious wastage of heat goes up the stack after the burner shuts 'ofi following each operating period. Various types of dampers are employed in an endeavour to reduce this heat loss but these mostly rely on the stack draft for operation with the result that they are held open whilst any considerable amount of heat remains in the furnace and so to a substantial degree fail to accomplish their intended object. An acknowledged ever-present difiiculty in smoke pipe dampers has been to assure in the interest of safety that the damper was open whenever the burner was operating.

These problems I have solved in my motor actuated smoke pipe damper that provides respectively full and controlled opening and closing of the smoke pipe immediately in advance of and a short time after each operation of the burner. The possibility of failure of the damper to open on the starting up of the burner I obviate by making the burner operation conditional on and subsequent to the opening of the damper, by inserting the damper in the motor circuit so that the motor circuit is completed by the damper mechanism on the damper reaching open position. Similarly, at the end of a run, the damper mechanism first breaks the burner circuit and then closes the damper valve in the smoke pipe. A time lag between breaking the burner circuit and closing the damper is allowed for purging the volatiles from the furnace but brief enough to trap and retain much heat that is normally dissipated.

The principal object of the invention is to provide an improved and positive acting, power actuated damper for the smoke pipe of a furnace or the like.

A further object of the invention is to provide an automatic, burner-fired furnace with a power controlled smoke pipe damper assuring safe operation at all times by eliminating the possibility of the burner coming on without the functioning of the damper opening mechanism.

A further object of the invention is to provide a simple, compact and moderately priced unit suitable for mounting on the smoke pipe.

170 the accomplishment of these and related objects as shall become apparent as the description proceeds, the invention resides in the construction, combination and arrangement of parts as shall be hereinafter more fully described, illustrated in the accompanying drawings, and pointed out in the claims hereunto appended.

The invention will be best understood and can be more clearly described when reference is had to the drawings forming a part of this disclosure wherein like characters indicate like parts throughout the several views.

In the drawings:

FIGURE 1 is a side elevation of my motor actuated damper unit applied to a smoke pipe;

FIGURE 2 is an end elevation thereof, as seen from the left side of FIGURE 1; and

FlGURE 3 is a simple wiring diagram for an automatic furnace burner under the control of my motor actuated damper.

Referring to the drawings, the preferred embodiment of the damper unit shown in FIGURES 1 and 2 employs 3,610,451 laten'ted Nov. 28, 1961 a simple frame 5 suspended from the smoke pipe 6 having depending arms 7 that encircle the smoke pipe and form the corners of the frame and support a floor or platform 8 at the bottom. In addition the corner arms 7, as will be seen especially in FIGURE 2, after encircling the pipe 6 depend vertically to a point below the bottom of the pipe and are offset inwardly to form confronting steps 9 that serve to support a heat insulating member 10 that underlies the smoke pipe as a shield.

An electrically operated damper motor 11 is mounted on a bracket member 12 rising from the frame platform 8 and securely clamped in selected rotative position by a tie band 13 connected to one or more of the frame corner posts 7. The motor shown is of a type in common use, being designed to operate on the low voltage output of a transformer and through hydraulic pressure on a diaphragm to project a plunger member 14 from its lower end into fully extended position and retain it there while the power is on, a spring being employed to retract the plunger when the motor circuit is broken. Alongside the plunger 14, a fulcrum post 15 depends from the motor and an arm 16 is pivoted thereon having one end connected to the motor plunger for vertically hinging operation thereby.

In the smoke pipe 6, a rocker shaft 17 carries a conventional butterfly damper valve 13, the shaft projecting through the pipe and having a radially extending arm 19 rigidly secured on one end. Suitable linkage such as the variable length push rod 20 connects the valve arm 19 and the power arm 16 hingedly actuated by the motor. The opposite ends of the rod fasten to the spaced valve and motor arms with adjustable ball and pivot joints 21 and 22 respectively. It will be clearly seen that when the motor 11 is energized the arm 16 is hinged on its fulcrum post 15 pushing the linkage rod 20 upwards and moving the smoke pipe butterfly valve 18 from closed to open position.

As it is intended to use this power actuated smoke pipe damper in association with an automatic gas or oil fueled furnace and the timing of the opening and closing of the smoke pipe valve with respect to the operation of the fuel burner is of critical importance, the circuit supplying the burner is put under the control of the damper in such a way that the burner circuit is only completed when the damper is approximately fully open. One way to do this is to insert a normally open microswitch 23 in the burner circuit and to mount this switch on the damper platform '8 where it is engaged by an actuating finger 24 projecting from the plunger end of the motor arm 16.

An explanatory wiring diagram is shown in FIGURE 3, indicating how the furnace burner is controlled by the damper to assure that the damper is open when the furnace burner is on and also is closed after the burner goes off, to trap as much useable heat in the furnace as possible, allowing only sufficient time lag for purging the furnace of volatiles. The burner motor circuit is served by a volt service line feeding through a safety limit control 2-6 and a primary burner control 27 thence to the burner ignition 28 and burner motor 29 but in the primary contnol 27 the circuit is interrupted by the normally open microswitch 23 associated with the damper unit. The low voltage circuit for the damper motor 11 is likewise served by a 110 volt service line but it passes first through a transformer 30 and a thermostat, aquastat or like heat responsive member 31.

Thus, in operation, it will be seen that when the heat responsive thermostat or aquastat 31 calls for heat by closing contacts in the usual way, it completes the low voltage circuit to the damper motor ll that operates causing the hinging arm 16 to open the valve 18 in the smoke pipe 6 and simultaneously, as the valve reaches approximately fully open position, the finger 24 on the' .run sufliciently to satisfy the heat responsive thermostat or aquastat control 31 it breaks the circuit to the damper motor 11 causing the plunger 14 to retract and the arm 16 to hinge and the initial movement of this arm allows the microswitch 23 to open and so breaks the furnace burner circuit and cuts off the fire. The damper motor arm 16 then continues to hinge slowly into inoperative position, closing the valve 18 in the smoke pipe. This closing interval consumes say some thirty seconds, during which the volatiles are purged from the furnace and allowed to escape up the chimney but the now closed damper traps most of the heat that was formerly lost up the stack.

From the foregoing description taken in connection with the accompanying drawings, it will be manifest that a smoke pipe damper is provided that will fulfill all the necessary requirements of such a device, but as many changes could be made in the above description and many apparently widely different embodiments of the invention may be constructed Within the scope of the appended claims, without departing fnom the spirit or scope thereof, it is intended that all matters contained in the said accompanying specification and drawings shall be interpreted as illustrative and not in a limitative or restrictive sense.

Having thus described the invention, what I claim as new is:

1. A motor actuated damper for a furnace smoke pipe comprising in combination 'with the pipe, a frame suspended below said pipe having spaced arms that extend over the pipe and depend therefrom to form corners of the frame and a horizontal platform supported by the lower ends of said arms, said arms depending vertically to a point below the bottom of said pipe and then being offset inwardly to provide confronting steps, a heat insulating member supported on the steps of said arms, a damper valve in said smoke pipe, a motor carried by said frame and shielded by said insulating member from the pipe above, an energizing circuit for said motor, and a damper valve actuator extending from said damper valve and operatively connected to said motor.

2. The structure of claim 1, wherein said motor is mounted on a bracket rising from said platform and is clamped in selected rotative position to one of the frame corner arms.

References Cited in the file of this patent UNITED STATES PATENTS 2,117,787 Bock May 17, 1938 2,165,488 Klimis July 11, 1939 2,224,705 Stringer Dec. 10, 1940 2,397,879 Morrow Apr. 2, 1946 2,856,992 Bartels Oct. 21, 1956. 

